Technological Field
The present invention relates to a transport member and a developing device including the transport member. More specifically, the present invention relates to a transport member that transports a developer by rotating in a predetermined rotation direction around a rotation axis, and a developing device including the transport member.
Description of the Related art
An electrophotographic image forming apparatus includes a facsimile machine, a copying machine, a printer, and a multifunction peripheral (MFP) having a scanner function, a facsimile function, a copying function, a function as a printer, a data communication function, and a server function, and the like.
An image forming apparatus generally forms a toner image by developing an electrostatic latent image formed on an image carrier with a developing device, transfers this toner image to a paper, and then forms an image on the paper by fixing the toner image onto the paper with a fixing device. In addition, some image forming apparatuses develop an electrostatic latent image on a surface of a photoreceptor by a developing device to form a toner image, transfer the toner image to an intermediate transfer belt by using a primary transfer roller, and secondary transfer the toner image on the intermediate transfer belt onto a paper by using a secondary transfer roller.
The developing device includes a replenishing portion, a developing tank, a stirring/transport member, a supply member, a developer carrier, and a regulating member. The developer replenished into the developing tank by the replenishing portion is stirred and transported by the stirring/transport member in the developing tank, and is supplied onto the developer carrier through the supply member. An excessive amount of the developer supplied onto the developer carrier is scraped off by the blade-like regulating member, and a transport amount is made uniform in a gap between the regulating member and the developer carrier. The uniformed developer is supplied from the developer carrier to the image carrier.
In a two-component electrophotographic method, the developer contains toner and carrier. The toner forms an image on a paper, and the carrier serves to carry the toner.
Conventional developing devices are disclosed in, for example, JP 2005-352042 A and JP 2016-099378 A. JP 2005-352042 A discloses a developing device including a stirring screw having a plurally wound blade fixed on an inner diameter side of a plurality of axially extending fins.
JP 2016-099378 A discloses a developing device including a screw configured by a rotating shaft, a blade that transports toner, and a stirring paddle. This developing device further includes a relief passage of an opening in order to lower a pressure generated in the blade and the paddle during operation, to avoid aggregation.
In recent years, as a size and weight of an image forming apparatus have been reduced, a size of a developing device is also reduced, and an amount of a developer filled in the developing device is also reduced. A developer stirring/transport member is provided with a screw to efficiently transport the developer, and a paddle is often provided on the screw in order to uniformly mix the developer.
However, in the prior art, it has been difficult to efficiently mix and transport the developer having a low toner/carrier ratio (hereinafter also referred to as a T/C ratio) returned from a developing roller to the stirring/transport member.
In the technology disclosed in JP 2005-352042 A, since the fins are provided on an outer periphery of the screw, an area of the screw is reduced. This lowers a transport velocity of the developer, taking time to replace the developer in the developing device. Further, immediately below the developing roller, the developer having a low T/C ratio returned from the developing roller may possibly rotate together with the blade, and be caught again by the developing roller. This may cause image defect, particularly in forming a solid image or the like.
In the technology of JP 2016-099378 A, while a stirring capacity of the developer is slightly improved since the opening is provided on the screw, a transport velocity of the developer is slowed down, taking time to replace the developer in the developing device.